Aussie boffins patent single-photon generator

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A group of Australian scientists has developed a new technique for producing single photons at room temperature, paving the way for real-world quantum cryptography. The research team already holds a worldwide patent on their invention, and has secured a AUD3.3m ($2.6m) grant from the Victorian government to develop their technology.

Scientists have known for some time that a laser beam can stimulate a diamond to emit single photons. Working from this starting point, Dr James Rabeau, a research fellow in the University of Melbourne's School of Physics, built a device that would send those single photons down an optical fibre.

Rabeau and co. used chemical vapour deposition to grow diamond crystals on the end of a section of optical fibre. The idea is that the laser will strike the diamond, stimulating the emission of a photon which will travel down the optical fibre as part of a message.

Quantum cryptography relies on the particle-like behaviour of light to secure transmission of data. Using the technology, two users can exchange secret keys, safe in the knowledge that no one could possible have eavesdropped on their 'conversation'.

Each bit of the key is encoded on a single photon. Intercepting that photon changes its polarisation, yielding no useful information to the eavesdropper and alerting the parties exchanging keys to the interception.

Rabeau's breakthrough is to have developed a cheap and reliable way of generating single photons, something he and his team says has not been possible up until now. However, as we reported last month, Toshiba has developed a single-photon-emitting LED, and numerous other products are available. ®